27 January 2025
Otago Fish & Game Council Media Release
Concern at major waterfowl kill from avian botulism
Otago Fish & Game is concerned about the first known major outbreak of avian botulism in the region that has led to more than 1000 dead and dying waterfowl at the Waikouaiti wastewater treatment plant.
The majority of the dead birds collected so far are paradise shelduck, a native taonga species which traditionally use oxidation ponds at the treatment plant as a moulting site.
Otago Fish & Game chief executive Ian Hadland said avian botulism outbreaks had occurred regularly in the North Island but were rare in the South Island.
“There is an increasing risk of further outbreaks this far south given climate change predictions and ongoing water quality issues,” Mr Hadland said.
“Fish & Game has been liaising with Dunedin City Council and other stakeholders concerning this outbreak, and we will continue to work with the DCC and other councils where appropriate.”
He said the primary task was to constrain the outbreak and minimise the harm to wider bird populations.
“We are pleased to see the DCC is taking a proactive role in removing dead birds to avoid further spread of the outbreak.”
Fish & Game staff are monitoring wetlands and estuaries nearby to see if the outbreak is spreading further.
“We understand that while avian botulism is often viewed as a ‘naturally’ occurring problem, measures can be taken to prevent or mitigate outbreaks,” he said.
“The organisation will be asking district councils across the region to look at their management plans for wastewater treatment plants to ensure everything is being done to minimise the risk and severity of harm to wildlife caused by avian botulism.”
While the majority of dead bird species are paradise shelduck, there are also native grey teal, mallard, Canada goose, black swan and black-backed gull.
More information:
- Outbreaks are triggered by a variety of environmental factors including high temperatures and low oxygen.
- The Waikouaiti wastewater treatment plant is one of dozens of Otago moulting sites for paradise shelduck, a taonga native species managed by Fish & Game.
- Paradise shelduck congregate in large numbers each summer to renew their flight feathers and are flightless for a period.
- Early last week Fish & Game counted approximately 1500 shelducks at the Waikouaiti treatment plant as part of annual aerial monitoring in the region.
- Many wastewater treatment plants provide the perfect microclimate for outbreaks to occur.
- The toxin from avian botulism can spread if birds eat maggots from infected carcasses.
- Avian botulism has killed an estimated 25,000 birds in the Auckland/Waikato region some years.
- Anyone who sees three or more sick or dead wild birds in a group is advised to report it immediately to Biosecurity New Zealand’s Exotic Pest and Disease Hotline on 0800 80 99 66.
